Radar system, integrated radar circuit and method for a radar system

ABSTRACT

A radar system includes a first integrated radar circuit having a plurality of first transmission paths and a local oscillator configured to generate a local oscillator signal. The first integrated radar circuit has a first terminal configured to output an oscillation signal based on the local oscillator signal. The radar system includes a second integrated radar circuit having a second transmission path and a second terminal. The radar system includes a partially reflective element coupled to the first terminal via a first line section and to the second terminal via a second line section. The partially reflective element is configured to reflect back a first portion of the oscillation signal as a reflected signal via the first line section to the first terminal and to pass on a second portion of the oscillation signal as a forward signal via the second line section to the second terminal.

FIELD

Exemplary embodiments relate to a radar system, an integrated radarcircuit, and a method for a radar system.

BACKGROUND

A multiplicity of transmission and reception channels are normally usedfor high-resolution radar systems. However, the number of possibletransmission and reception channels of a single monolithic microwaveintegrated circuit (MMIC) is limited. Therefore, a plurality of MMICsare often cascaded, i.e. a plurality of radar transceiver MMICs arecoupled, wherein one of the MMICs serves as master and provides thesystem clock, the trigger line, the radio-frequency transmission signal,etc. In order to enable correct operation of the radar system, theradio-frequency transmission signals of the channels distributed amongthe individual MMICs need to be synchronized

SUMMARY

There is thus a need to provide an improved technology for thesynchronization of integrated radar circuits.

The need can be met by the subject matter of the patent claims.

One exemplary embodiment relates to a radar system. The radar systemincludes a first integrated radar circuit having a plurality of firsttransmission paths and a local oscillator configured to generate a localoscillator signal. The first integrated radar circuit additionally has afirst terminal configured to output an oscillation signal based on thelocal oscillator signal. The radar system furthermore includes a secondintegrated radar circuit having at least one second transmission pathand a second terminal. Furthermore, the radar system includes apartially reflective element coupled to the first terminal via a firstline section and to the second terminal via a second line section. Thepartially reflective element is configured to reflect back a firstportion of the oscillation signal as a reflected signal via the firstline section to the first terminal and to pass on a second portion ofthe oscillation signal as a forward signal via the second line sectionto the second terminal. The first integrated radar circuit furthermoreincludes a directional coupler, which is coupled to the first terminalvia a first port and is configured to output the reflected signal via asecond port to a signal node of the first integrated radar circuit. Thefirst transmission paths are coupled to the signal node and at least oneportion of the first transmission paths is configured to generate radartransmission signals on the basis of the reflected signal.

A further exemplary embodiment relates to an integrated radar circuit.The integrated radar circuit includes a plurality of transmission pathsand a local oscillator configured to generate a local oscillator signal.Furthermore, the integrated radar circuit includes a terminal forlinking an external element via a line section. The terminal isconfigured to output an oscillation signal based on the local oscillatorsignal to the line section and to receive a portion of the oscillationsignal reflected by the external element as a reflected signal via theline section. Furthermore, the integrated radar circuit includes adirectional coupler, which is coupled to the terminal via a first portand is configured to output the reflected signal via a second port to asignal node of the integrated radar circuit. The transmission paths arecoupled to the signal node and at least one portion of the transmissionpaths is configured to generate radar transmission signals on the basisof the reflected signal.

In addition, one exemplary embodiment relates to a method for a radarsystem having a first integrated radar circuit including at least aplurality of first transmission paths, a local oscillator and a firstterminal, and a second integrated radar circuit including at least onesecond transmission path and a second terminal. The method includesoutputting an oscillation signal based on a local oscillator signal ofthe local oscillator via the first terminal to a partially reflectiveelement coupled to the first terminal via a first line section and tothe second terminal via a second line section. Furthermore, the methodincludes reflecting back a first portion of the oscillation signal as areflected signal via the first line section to the first terminal bymeans of the partially reflective element. Furthermore, the methodincludes passing on a second portion of the oscillation signal as aforward signal via the second line section to the second terminal bymeans of the partially reflective element. The method furthermoreincludes outputting the reflected signal via a second port of adirectional coupler of the first integrated radar circuit to a signalnode of the first integrated radar circuit. A first port of thedirectional coupler is coupled to the first line section. Furthermore,the method includes generating radar transmission signals on the basisof the reflected signal by means of at least one portion of the firsttransmission paths coupled to the signal node.

BRIEF DESCRIPTION OF THE DRAWINGS

Some examples of devices and/or methods are explained in greater detailmerely by way of example below with reference to the accompanyingfigures, in which:

FIG. 1 shows a first exemplary embodiment of a radar system;

FIG. 2 shows a second exemplary embodiment of a radar system;

FIG. 3 shows a first exemplary embodiment of a directional coupler;

FIG. 4 shows a second exemplary embodiment of a directional coupler;

FIG. 5 shows a third exemplary embodiment of a directional coupler;

FIG. 6 shows one exemplary embodiment of a partially reflective element;

FIGS. 7-1 and 7-2 show a third exemplary embodiment of a radar system;and

FIG. 8 shows a flow diagram of one exemplary embodiment of a method fora radar system.

DETAILED DESCRIPTION

Various examples will now be described more thoroughly with reference tothe accompanying figures, in which some examples are illustrated. In thefigures the thicknesses of lines, layers and/or regions may beexaggerated for elucidation purposes.

While further examples are suitable for various modifications andalternative forms, some specific examples thereof are accordingly shownin the figures and described thoroughly below. However, this detaileddescription does not limit further examples to the specific formsdescribed. Further examples can cover all modifications, counterpartsand alternatives that fall within the scope of the disclosure.Throughout the description of the figures, identical or similarreference signs refer to identical or similar elements which can beimplemented identically or in modified form in a comparison with oneanother, while they provide the same or a similar function.

It goes without saying that if one element is designated as “connected”or “coupled” to another element, the elements can be connected orcoupled directly or via one or more intermediate elements. If twoelements A and B are combined using an “or”, this should be understoodsuch that all possible combinations are disclosed, i.e. only A, only B,and A and B, unless explicitly or implicitly defined otherwise. Analternative wording for the same combinations is “at least one from Aand B” or “A and/or B”. The same applies, mutatis mutandis, tocombinations of more than two elements.

The terminology used here for describing specific examples is notintended to be limiting for further examples. If a singular form, e.g.“a, an” and “the”, is used and the use of only a single element isdefined neither explicitly nor implicitly as obligatory, furtherexamples can also use plural elements in order to implement the samefunction. If a function is described below as being implemented using aplurality of elements, further examples can implement the same functionusing a single element or a single processing entity. Furthermore, itgoes without saying that the terms “comprises”, “comprising”, “has”and/or “having” in their usage indicate with greater precision thepresence of the specified features, integers, steps, operations,processes, elements, components and/or a group thereof, but do notexclude the presence or the addition of one or more other features,integers, steps, operations, processes, elements, components and/or agroup thereof.

Unless defined otherwise, all terms (including technical and scientificterms) are used here in their customary meaning in the field with whichexamples are associated.

FIG. 1 shows a radar system 100 comprising a first integrated radarcircuit 110 and a second integrated radar circuit 120. By way ofexample, the integrated radar circuits 110 and 120 can be embodied asMMICs. The first integrated radar circuit 110 serves as master, whilethe second integrated radar circuit 120 serves as slave. The twointegrated radar circuits 110 and 120 are formed on differentsemiconductor chips.

The first integrated radar circuit 110 comprises a plurality of firsttransmission paths 111 in order to generate radar transmission signals117 (e.g. having a carrier frequency of approximately 77 GHz). Thesecond integrated radar circuit 120, too, comprises at least one secondtransmission path 121 in order to generate a radar transmission signal123. A plurality of radar transmission signals can thus be generated bymeans of the integrated radar circuits 110 and 120 in order to enablehigh-resolution radar scanning of an environment of the radar system100.

Furthermore, the first integrated radar circuit 110 comprises a localoscillator 113 configured to generate a local oscillator signal 114. Thelocal oscillator signal 114 can be frequency-modulated for example (e.g.in order to emit chirp signals in the region of 77 GHz). The localoscillator signal 114 serves as a basis for the synchronous generationof the radar transmission signals in the two integrated radar circuits110 and 120.

For synchronizing the two integrated radar circuits 110 and 120 on thebasis of the local oscillator signal 114, the first integrated radarcircuit 110 additionally comprises a first terminal 112 configured tooutput an oscillation signal based on the local oscillator signal 114.The oscillation signal based on the local oscillator signal 114 can befor example the local oscillator signal 114 itself or a signal derivedfrom the local oscillator signal 114. By way of example, the oscillationsignal can have a lower frequency than the local oscillator signal 114and be a divided-down local oscillator signal (e.g. a radio-frequencysignal having half or one quarter of the frequency of the localoscillator signal 114). The oscillation signal can likewise be e.g. apower-amplified (and optionally filtered) copy of the local oscillatorsignal 114. The oscillation signal can be applied to the terminal 112for example by the local oscillator 113 or by a circuit component of thefirst integrated radar circuit 110 that generates the oscillation signalon the basis of the local oscillator signal 114.

For coupling the second integrated radar circuit 120 to the firstintegrated radar circuit 110, the second integrated radar circuit 120comprises a second terminal 122.

A partially reflective element 130 is coupled between the firstintegrated radar circuit 110 and the second integrated radar circuit120. The partially reflective element 130 is coupled to the firstterminal 112 via a first line section 140 and to the second terminal 122via a second line section 150. Correspondingly, the partially reflectiveelement 130 receives the oscillation signal present at the firstterminal 112 via the first line section 140. The partially reflectiveelement 130 is thus connected between the terminals 112 and 122. Theline sections 140 and 150 can be for example strip lines, waveguides ordielectric waveguides. The line sections 140 and 150 can extend forexample on a circuit board or some other carrier on which the radarcircuits 110 and 120 are secured.

The partially reflective element 130 is configured to reflect back afirst portion of the oscillation signal as a reflected signal via thefirst line section 140 to the first terminal 112 and to pass on a secondportion of the oscillation signal as a forward signal via the secondline section 150 to the second terminal 122. In other words: one part ofthe oscillation signal is reflected back to the first integrated radarcircuit 110 by the partially reflective element 130, while another partpasses through the partially reflective element 130 and reaches thesecond integrated radar circuit 120 via the second line section 150.

The first integrated radar circuit 110 comprises a directional coupler115, which is coupled to the first terminal 112 (or the first linesection 140) via a first port and is configured to output the reflectedsignal via a second port to a signal node 116 of the first integratedradar circuit 110. On account of the directional characteristic of thedirectional coupler 115, the reflected signal can be output to thesignal node 116 substantially without constituents of further signalcomponents present at the first terminal 112. In other words: thedirectional coupler 115 can enable an output coupling of the reflectedsignal from the totality of all the signals present at the firstterminal 112.

The first transmission paths 111 are coupled to the signal node and canthereby obtain the reflected signal. At least one portion of the firsttransmission paths 111 is configured to generate radar transmissionsignals 117 on the basis of the reflected signal. By way of example, insome exemplary embodiments, only one portion of the first transmissionpaths 111 can be configured (or be driven) to generate radartransmission signals 117 on the basis of the reflected signal.Alternatively, it is also possible for all the transmission paths 111 tobe configured to generate radar transmission signals 117 on the basis ofthe reflected signal. Consequently, the portion of the firsttransmission paths 111 which generates the radar transmission signals117 can generate the radar transmission signals 117 in a mannertemporally correlated with the reflected signal.

The at least one second transmission path 121 of the second integratedradar circuit 120 is coupled to the second terminal 122 and can thusobtain the forward signal. The at least one second transmission path 121is configured to generate the radar signal 123 on the basis of theforward signal. By way of example, the received forward signal can befed to one or more power amplifiers in order to generate thetransmission signal 123. If the received forward signal is based on adivided-down local oscillator signal, then a frequency multiplier can beprovided in the radar circuit 120 in order to obtain the frequency ofthe local oscillator signal again. The second transmission path 121 canthus generate the radar transmission signal 123 in a manner temporallycorrelated with the forward signal.

The two integrated radar circuits 110 and 120 can be synchronized bymeans of the partial reflection of the oscillation signal in theradio-frequency range since a portion of the oscillation signal is thusrespectively provided to both integrated radar circuits 110 and 120. Inthis case, only a single terminal is necessary in the integrated radarcircuit 110 in order to output the oscillation signal used for thesynchronization and to receive the reflected portion of said oscillationsignal.

Besides the synchronization of transmission paths 111 and 121, thereflected signal and the forward signal can also be used forsynchronizing reception paths of the two integrated radar circuits 110and 120.

By way of example, the first integrated radar circuit 110 can have atleast one first reception path 118 coupled to the signal node 115, andthe second integrated radar circuit 120 can furthermore have at leastone second reception path 124 coupled to the second terminal 122 for thereception and the processing of radar reception signals.Correspondingly, the at least one first reception path 118 is configuredto down-convert a received radar reception signal 119 using thereflected signal (i.e. to down-convert the radar reception signal 119 ina manner temporally correlated with the reflected signal), while the atleast one second reception path 124 is configured to down-convert areceived radar reception signal 125 using the forward signal (i.e. theradar reception signal 125 is down-converted in a manner temporallycorrelated with the forward signal).

The partially reflective element 130 is configured to generate thereflected signal and the forward signal with a constant phase anglerelative to one another. If φ₁₁(f) denotes the phase of the reflectedsignal and φ₂₁(f) denotes the phase of the forward signal, the followingrelationship thus holds true:

$\begin{matrix}{\frac{\varphi_{11}(f)}{\varphi_{21}(f)} = {{const}.}} & (1)\end{matrix}$

By way of example, the partially reflective element 130 can beconfigured to generate the reflected signal and the forward signal inphase, such that φ₁₁(f)=φ₂₁(f). Alternatively, the partially reflectiveelement 130 can be configured to generate the reflected signal with afixed phase offset c relative to the forward signal, such thatφ₁₁(f)=φ₂₁(f)+c.

In order to enable the synchronism of the two integrated radar circuits110 and 120, the phases of the reflected signal and of the forwardsignal when they reach the terminals 112 and 122, respectively, shouldbe (as far as possible) identical. The phases of the reflected signaland of the forward signal upon reception of the signals at the terminals112 and 122, respectively, are determined not only by the partiallyreflective element 130, but also by the lengths of the two line sections140 and 150. Correspondingly, the lengths of the first line section 140and of the second line section 150 can be chosen such that a phase ofthe reflected signal upon reception at the first terminal 112 isidentical to a phase of the forward signal upon reception at the secondterminal 122.

By way of example, the first line section 140 and the second linesection 150 can have the same electrical length and the sameconstitution if the partially reflective element 130 generates thereflected signal and the forward signal in phase. In other words: thepartially reflective element 130 can be arranged centrally within thetwo terminals 112 and 122.

If the partially reflective element 130 generates the reflected signalwith a phase offset relative to the forward signal, e.g. one of the twoline sections 140 and 150 can be longer than the other in order tobalance or to compensate for the phase offset generated by the partiallyreflective element 130. In other words: the partially reflective element130 can be arranged offset with respect to the center of the lineconnecting the two terminals 112 and 122.

The partially reflective element 130 can likewise be embodied such thatthe reflected signal and the forward signal have similar signalstrengths. By way of example, the partially reflective element 130 canbe configured to partly reflect the oscillation signal in such a waythat respective signal strengths of the reflected signal and of theforward signal deviate from one another by less than 90%, 80%, 70%, 60%,50%, 40%, 30%, 20% or 10%. In some exemplary embodiments, the partiallyreflective element 130 can be configured to partly reflect theoscillation signal in such a way that respective signal strengths of thereflected signal and of the forward signal are (substantially)identical. If S₁₁ describes the scattering parameter of the reflectedsignal, i.e. the input reflection factor of the partially reflectiveelement 130, and S₂₁ describes the scattering parameter of the forwardsignal, i.e. the forward transmission factor of the partially reflectiveelement 130, the following relationship can thus hold true:S ₁₁ =S ₂₁  (2)

By way of example, the reflected signal and the forward signal can eachhave a signal strength of −3 dBm if a power of 0 dBm is present at thefirst line section 140 (i.e. S₁₁=S₂₁=−3 dB).

In some exemplary embodiments, the reflected signal can thus be(substantially) identical to the forward signal, such that the firstintegrated radar circuit 110 effectively receives the same signal as thesecond integrated radar circuit 120. The two integrated radar circuits110 and 120 can thus be synchronized to the same signal. In other words:the master MMIC 110 and the slave MMIC 120 can be phase-synchronized bymeans of the oscillation signal in the radio-frequency range. Theproposed synchronization architecture uses the reflected portion of theoscillation signal as feedback for the master MMIC 110, such that themaster MMIC 110 can be kept synchronous with the slave MMIC 120. Thisalso makes it possible, for example, that the channels of the masterMMIC 110 and of the slave MMIC 120 can be operated in an MIMO (MultipleIn Multiple Out) system. In contrast to existing concepts forself-supply with local oscillation signals, a single terminal at themaster MMIC 110 is sufficient for the proposed synchronizationarchitecture.

The oscillation signal can be applied to the first terminal 112 via thedirectional coupler 115, for example. The directional coupler can beconfigured, for example, to receive the oscillation signal via a thirdport from the local oscillator 115 or some other circuit element of thefirst integrated radar circuit 110 and to output said signal via thefirst port to the first line section 140 or the first terminal 112.Alternatively, the oscillation signal can for example also be coupled inor applied to the first terminal 112 via a coupling-in element (notillustrated) arranged between the directional coupler 115 and the firstterminal 112.

In accordance with some exemplary embodiments, the two integrated radarcircuits 110 and 120 can (temporarily or permanently) swap their rolesas master and slave, respectively. By way of example, in the case of adefect at the local oscillator 113, the first integrated radar circuit110 can change from being the master to being the slave and, conversely,the second integrated radar circuit 120 can change from being the slaveto being the master. To put it more generally, in a further operatingmode of the radar circuit 100 the local oscillator 113 of the firstintegrated radar circuit 110 can be inactive. The second integratedradar circuit 120 can have a further local oscillator 126, which in thefurther operating mode is configured to generate a further localoscillator signal 127. The second terminal 122 in the further operatingmode is configured to output a further oscillation signal based on thefurther local oscillator signal. The synchronization of the twointegrated radar circuits 110 and 120 can take place analogously to theabove-described concept in the further operating mode, too. In thisregard, the partially reflective element 130 in the further operatingmode can be configured to reflect back a first portion of the furtheroscillation signal as a further reflected signal via the second linesection 150 to the second terminal 122 and to pass on a second portionof the further oscillation signal as a further forward signal via thefirst line section 140 to the first terminal 112.

One portion of the first transmission paths 111 in the further operatingmode can correspondingly be configured to generate the radartransmission signals 117 in a manner temporally correlated with thefurther forward signal, and the at least one second transmission path121 in the further operating mode can correspondingly be configured togenerate the radar transmission signal 123 in a manner temporallycorrelated with the further reflected signal. In this regard, the radarsystem 100 can continue to be operated e.g. even in the event of afailure of the local oscillator 113.

In the exemplary embodiment illustrated in FIG. 1, one slave MMIC iscoupled to the master MMIC. In accordance with one exemplary embodiment,it is also possible for a plurality of slave MMICs to be coupled to themaster MMIC (e.g. two, three, four or more slave MMICs). This isillustrated by way of example in FIG. 2. In comparison with the radarsystem 100 illustrated in FIG. 1, the radar system 200 illustrated inFIG. 2 has an additional third integrated radar circuit 270. The thirdintegrated radar circuit 270 comprises a third terminal 272 and at leastone third transmission path 271 in order to generate a radartransmission signal 273.

The partially reflective element 230 is coupled to the third terminal272 via a third line section 260. In order to synchronize the thirdintegrated radar circuit 270 with the other two integrated radarcircuits 110 and 120, the partially reflective element 230 isfurthermore configured to pass on a third portion of the oscillationsignal as a further forward signal via the third line section 260 to thethird terminal 272. The at least one third transmission path 271 iscoupled to the third terminal 272 and is configured to generate theradar transmission signal 273 in a manner temporally correlated with thefurther forward signal.

Besides the synchronization of the transmission paths 111, 121 and 271,the reflected signal and the forward signal can also be used forsynchronizing reception paths of the integrated radar circuits 110, 120and 270. By way of example, the third integrated radar circuit 270 canfurthermore comprise at least one third reception path 274 which iscoupled to the third terminal 272 and is configured to down-convert aradar reception signal 275 using the further forward signal (i.e. todown-convert the radar reception signal 275 in a manner temporallycorrelated with the further forward signal).

In order to enable a reliable synchronization of all three integratedradar circuits 110, 120 and 270, the partially reflective element 230 isconfigured to generate the reflected signal, the forward signal and thefurther forward signal with a constant phase angle relative to oneanother. By way of example, in some exemplary embodiments, the partiallyreflective element 230 can be configured to generate the reflectedsignal, the forward signal and the further forward signal in phase, suchthat φ₁₁(f)=φ₂₁(f)=φ₃₁(f), wherein φ₃₁(f) denotes the phase of thefurther forward signal. Alternatively, the partially reflective element230 can be configured to generate the reflected signal, the forwardsignal and the further forward signal with fixed phase offsets c and d,respectively, relative to one another, such thatφ₁₁(f)=φ₂₁(f)+c=φ₃₁(f)+d.

The setting of the phases of the reflected signal, of the forward signaland of the further forward signal can once again additionally bedetermined by way of the lengths of the line sections 140, 150 and 260.Correspondingly, the lengths of the first line section 140, of thesecond line section 150 and of the third line section 260 can be chosensuch that a phase of the reflected signal upon reception at the firstterminal 112 is identical to a phase of the forward signal uponreception at the second terminal 122 and to a phase of the furtherforward signal upon reception at the third terminal 272. By way ofexample, the line sections 140, 150 and 260 can have the same length.Alternatively, one or more of the line sections 140, 150 and 260 can bechosen to be longer than the other line sections 140, 150 and 260.

With regard to the signal strengths of the reflected signal, of theforward signal and of the further forward signal, the explanation givenabove in association with FIG. 1 is substantially applicable. By way ofexample, the partially reflective element 230 can be configured topartly reflect the oscillation signal in such a way that respectivesignal strengths of the reflected signal, of the forward signal and ofthe further forward signal deviate from one another by less than 90%,80%, 70%, 60%, 50%, 40%, 30%, 20% or 10%. In some exemplary embodiments,the partially reflective element 230 can be configured to partly reflectthe oscillation signal in such a way that respective signal strengths ofthe reflected signal, of the forward signal and of the further forwardsignal are (substantially) identical. By way of example, the followingrelationship can hold true:S ₁₁ =S ₂₁ =S ₃₁=−3 dB  (3),wherein S₃₁ denotes the scattering parameter of the further forwardsignal, i.e. the forward transmission factor of the partially reflectiveelement 230 toward the third terminal 272.

As already described in association with FIG. 2 for the secondintegrated radar circuit 120, in some exemplary embodiments, the thirdintegrated radar circuit 270, too, can be operated as master instead ofas slave, i.e. can generate a local oscillation signal and output anoscillation signal based thereon to the partially reflective element 230for the synchronization of the integrated radar circuits 110, 120 and270. In order to avoid unnecessary repetitions, therefore, reference ismade to the above explanations concerning the second integrated radarcircuit 120, which correspondingly also hold true for the thirdintegrated radar circuit 270.

In accordance with some exemplary embodiments, the integrated radarcircuits 110, 120 and 270 illustrated in FIGS. 1 and 2 can beconstructed identically (e.g. be identical to MMICs) and differ merelywith regard to the operating mode used (master and slave, respectively).In other exemplary embodiments, however, different MMICs can also beused.

Some exemplary directional couplers which can be used for the proposedsynchronization architecture are described below in association withFIGS. 3 to 5.

FIG. 3 shows a rat-race coupler 300 having a ring conductor 310 and fourports P1, P2, P3 and P4. The oscillation signal is present at the portP1 (i.e. the port P1 is coupled to the source of the oscillationsignal), while the port P2 is coupled to the first terminal of the firstintegrated radar circuit or the partially reflective element. The portP3 is coupled to the signal node of the first integrated radar circuitand the port P4 is isolated. The distances between the ports P1 and P4,P4 and P3, and P4 and P2, are in each case ¼ of the wavelength λ used(i.e. the wavelength of the oscillation signal). The distance betweenthe ports P1 and P2 is ¾ of the wavelength λ. Good isolation between theports P1 and P3 is correspondingly provided, such that the scatteringparameters S₁₃=S₃₁ are very low. Substantially only the reflected signalreceived via the port P2 is thus present at the port P3.

FIG. 4 shows a branch-line coupler 400 having four ports P1, P2, P3 andP4. The oscillation signal is present at the port P1 (i.e. the port P1is coupled to the source of the oscillation signal), while the port P2is coupled to the first terminal of the first integrated radar circuitor the partially reflective element. The port P3 is isolated and theport P4 is coupled to the signal node of the first integrated radarcircuit. The distances between the ports are in each case ¼ of thewavelength λ used. Good isolation between the ports P1 and P4 iscorrespondingly provided, such that the scattering parameters S₁₄=S₄₁are very low. Substantially only the reflected signal received via theport P2 is thus present at the port P4.

The directional couplers shown in FIGS. 3 and 4 thus both have goodisolation between the ports for feeding in the oscillation signal andbranching off the reflected signal. A further directional coupler, whichcan make possible lower signal losses in comparison with the directionalcouplers shown in FIGS. 3 and 4, is illustrated in FIG. 5. FIG. 5 showsa further rat-race coupler 500, wherein, in comparison with the rat-racecoupler 300, a biasable PIN diode 520 (Positive Intrinsic NegativeDiode) is arranged between the third port P3, which is coupled to thesignal node, and the ring conductor 510. Via a bias voltage circuit (notillustrated), a bias voltage can be applied to the PIN diode 520, suchthat the PIN diode 520 can be operated as a controllable resistor. Forthis purpose, a corresponding control logic for setting purposes can beconnected to the PIN diode 520. The PIN diode 520 can thus be used as anamplitude regulator for the reflected signal present at the port P3. ThePIN diode 520 can likewise also be used as a radio-frequency switch andcan thus separate the channels P3 and P4 from the switching circuit viaa control logic. Consequently, less power is lost through the structureitself and it is possible to use the channel as a transmission channelas well. In other exemplary embodiments, other active elements can alsobe provided.

A biasable PIN diode 530 is likewise arranged between the isolated,fourth port P4 of the rat-race coupler 500 and the ring conductor 510.

However, the directional coupler used for the proposed synchronizationarchitecture is not restricted to the directional couplers describedabove in association with FIGS. 3 to 5. Rather, any other suitabledirectional coupler can also be used.

Another exemplary implementation for the partially reflective element issubsequently shown in FIG. 6. By way of example, the partiallyreflective element can be embodied as a butterfly stub 600. By way ofthe setting of the radius Ro and the angle of the circle-segment-shapedstubs 610 and 620, a desired impedance mismatch can be generated in thelines connecting the integrated radar circuits in order thus to reflectback a portion of the oscillation signal arriving from the firstterminal with the desired phase and/or signal strength characteristicsand to allow a further portion of the arriving oscillation signal withthe desired phase and/or signal strength characteristics to pass to thesecond terminal.

However, the partially reflective element used for the proposedsynchronization architecture is not restricted to the butterfly stub600. Rather, any other suitable element can also be used (e.g. a coupleror power divider).

In some exemplary embodiments, the partially reflective element can beformed exclusively by passive components. In this case, the reflectioncan result as a consequence of a geometric structure that is adaptedwith respect to the wavelengths of the oscillation signal. By way ofexample, a ring structure or an impedance mismatch structure whichdiffers from the line sections can be used in order to achieve both apartial reflection and passing on in the forward direction by means ofsuitable choice of the geometric dimensions. By comparison withpartially reflective elements having active components, it is possiblein this way to achieve greater robustness and to reduce a probability offailure of the partially reflective element.

FIGS. 7-1 and 7-2 shows a further exemplary embodiment of a radarsystem. FIGS. 7-1 and 7-2 illustrate one radar system 700 extendedacross two sheets. As such, lines that terminate at the dashed-line inone figure are continued at the dashed-line in the other figure. Theradar system 700 comprises a first integrated radar circuit 710 and asecond integrated radar circuit 720. The first integrated radar circuit710 serves as master, while the second integrated radar circuit 720serves as slave.

The first integrated radar circuit 710 comprises a plurality of firsttransmission paths 711-1, 711-2 and 711-3 and a plurality of firstreception paths 714-1, 714-2, 714-3 and 714-4. The second integratedradar circuit 720 likewise comprises a plurality of second transmissionpaths 721-1 and 721-2 and a plurality of second reception paths 724-1,724-2, 724-3 and 724-4.

Furthermore, the first integrated radar circuit 710 comprises a localoscillator 713 configured to generate a local oscillator signal 714.

For synchronizing the two integrated radar circuits 710 and 720 on thebasis of the local oscillator signal 714, the first integrated radarcircuit 710 additionally comprises a first terminal 712-1 configured tooutput an oscillation signal based on the local oscillator signal 714.The first terminal 712-1 is coupled to the local oscillator 713 via thefirst transmission path 711-1. In other words: one of the firsttransmission paths 711-1, 711-2 and 711-3 is coupled to the firstterminal 712-1 and is configured to apply the oscillation signal basedon the local oscillator signal 714 to the first terminal 712-1. By wayof example, the first transmission path 711-1 can filter and amplify thelocal oscillator signal 714 and apply the local oscillator signal thathas been processed in this way as oscillation signal to the firstterminal 712-1. The oscillation signal is applied to the first terminal712-1 via a directional coupler 715, which is coupled to the firstterminal 712-1 via a first port and is coupled to the first transmissionpath 711-1 via a third port.

For coupling the second integrated radar circuit 720 to the firstintegrated radar circuit 710, the second integrated radar circuit 720comprises a second terminal 722-1.

A partially reflective element 730 is coupled between the firstintegrated radar circuit 710 and the second integrated radar circuit720. The partially reflective element 730 is coupled to the firstterminal 712 via a first line section 740 and to the second terminal722-1 via a second line section 750. Correspondingly, the partiallyreflective element 730 receives the oscillation signal present at thefirst terminal 712 via the first line section 740.

The partially reflective element 730 is configured to reflect back afirst portion of the oscillation signal as a reflected signal via thefirst line section 740 to the first terminal 712 and to pass on a secondportion of the oscillation signal as a forward signal via the secondline section 750 to the second terminal 722. In other words: one part ofthe oscillation signal is reflected back to the first integrated radarcircuit 710 by the partially reflective element 730, while another partpasses through the partially reflective element 730 and reaches thesecond integrated radar circuit 720 via the second line section 750.

Although the first line section 740 is represented by two lines in FIG.7, the first line section 740 is a single signal line. Therepresentation of the first line section 740 by two lines was chosen inorder to illustrate that both a forward component (namely theoscillation signal) and a backward component (namely the reflected-backportion of the oscillation signal) are transferred simultaneously viathe first line section 740 between the first terminal 712-1 and thepartially reflective element 730.

Via a second port of the directional coupler 115, the reflected signalis output to a signal node 716 of the first integrated radar circuit710. Output coupling of the reflected signal from the totality of allthe signals present at the first terminal 112 is thus carried out bymeans of the directional coupler 115.

The other first transmission paths 711-2 and 711-3 are likewise coupledto the signal node 716 and obtain the reflected signal via the latter.Consequently, the first transmission paths 711-2 and 711-3 can generateradar transmission signals in a manner temporally correlated with thereflected signal and output them via terminals 712-2 and 712-3,respectively, to transmission antennas for emission into thesurroundings. Moreover, the first reception paths 714-1, 714-2, 714-3and 714-4 are coupled to the signal node 716 and thus obtain thereflected signal. Consequently, the first reception paths 714-1, 714-2,711-3 and 714-4 can down-convert radar reception signals received fromreception antennas via terminals 717-1, 717-2, 717-3 and 717-4 using thereflected signal or can down-convert the radar reception signals in amanner temporally correlated with the reflected signal.

The second transmission paths 721-1 and 721-2 of the second integratedradar circuit 720 are coupled to the second terminal 722-1 and thusobtain the forward signal. The second transmission paths 721-1 and 721-2can thus generate radar transmission signals in a manner temporallycorrelated with the forward signal and output them via terminals 722-2and 722-3, respectively, to transmission antennas for emission into thesurroundings. Furthermore, the second reception paths 724-1, 724-2,724-3 and 724-4 are coupled to the second terminal 722-1 and obtain theforward signal via the latter. Consequently, the second reception paths724-1, 724-2, 724-3 and 724-4 can down-convert radar reception signalsreceived from reception antennas via terminals 723-1, 723-2, 723-3 and723-4 using the forward signal or can down-convert the radar receptionsignals in a manner temporally correlated with the forward signal.

As already explained above in association with FIG. 1, the reflectedsignal can be (substantially) identical to the forward signal, such thatthe first integrated radar circuit 710 effectively receives the samesignal as the second integrated radar circuit 720. The two integratedradar circuits 710 and 720 can thus be synchronized orphase-synchronized to (substantially) the same signal in theradio-frequency range. In contrast to existing concepts for self-supplywith local oscillation signals, a single terminal at the integratedradar circuit 710 is sufficient for the proposed synchronizationarchitecture.

Besides the oscillation signal for the phase synchronization in theradio-frequency range, the two integrated radar circuits 710 and 720 canalso exchange one or more further signals for synchronization. By way ofexample, the first integrated radar circuit 710 can output a systemclock via further terminals 712-5 and 712-6, which are received by thesecond integrated radar circuit 720 via terminals 722-5 and 722-6coupled to the terminals 712-5 and 712-6. Correspondingly, bothintegrated radar circuits 710 and 720 can operate with the same systemclock. Likewise, via a further terminal 712-4, the first integratedradar circuit 710 can output a trigger signal for ramping up the radartransmission signals in the frequency range, which trigger signal isreceived via a terminal 722-4 of the second integrated radar circuit720, said terminal being coupled to the terminal 712-4. Correspondingly,ramping up the radar transmission signals can be carried outsynchronously in both integrated radar circuits 710 and 720.

The two integrated radar circuits 710 and 720 can additionally havefurther terminal, such as, for instance, a (high-speed) interface 719-1and 729-1, respectively, for outputting the down-converted radarreception signals or serial buses (e.g. a serial peripheral interface)for exchanging other data.

In some exemplary embodiments, the integrated radar circuits 710 and 720can likewise also be operated by themselves. By way of example, thefirst integrated radar circuit 710 can be used by itself (i.e. withoutthe integrated radar circuit 720). In this operating mode, asynchronization of the first integrated radar circuit 710 with thesecond integrated radar circuit is not necessary. Correspondingly, thefirst transmission path 711-1 can also be used for generating a radartransmission signal in this operating mode.

By way of example, the first integrated radar circuit 720 canfurthermore comprise a switch (not shown) configured to couple the localoscillator 713 to the signal node 716 in the further operating mode,such that all the first transmission paths 711-1, 711-2 and 711-3 thenreceive the local oscillator signal 714. Correspondingly, the firsttransmission path 711-1 in the further operating mode can be configuredto generate a radar transmission signal based on the local oscillatorsignal 714 and to output it to the first terminal 712-1. In the furtheroperating mode, the first terminal 712-1 is coupled to a transmissionantenna instead of the partially reflective element 730. The othertransmission paths 711-2 and 711-3 in the further operating mode areconfigured to generate the radar transmission signals based on the localoscillator signal 714. Correspondingly, during individual operation ofthe first integrated radar circuit 710, all the transmission paths canbe used for generating radar transmission signals.

In accordance with some exemplary embodiments, the integrated radarcircuits 710, 720 can be structured identically (e.g. be identicalMMICs) and differ merely with regard to the operating mode used (masterand slave, respectively). By way of example, the second integrated radarcircuit 720 can also have a local oscillator and/or a furthertransmission path, which is (are) coupled to the second terminal 722-1via a directional coupler, such that, analogously to the aboveexplanations for the first integrated radar circuit 710, the secondterminal 722-1 can be used both for receiving the forward signal incascaded operation and for outputting a radar transmission signal duringindividual operation of the second integrated radar circuit 720.

In order once again to summarize the above-described aspects concerningthe synchronization of integrated radar circuits, FIG. 8 also shows aflow diagram of a method 800 for a radar system. The radar systemcomprises a first integrated radar circuit, comprising at least aplurality of first transmission paths, a local oscillator and a firstterminal, and a second integrated radar circuit comprising at least onesecond transmission path and a second terminal.

The method 800 comprises outputting 802 an oscillation signal based on alocal oscillator signal of the local oscillator via the first terminalto a partially reflective element coupled to the first terminal via afirst line section and to the second terminal via a second line section.Furthermore, the method 800 comprises reflecting back 804 a firstportion of the oscillation signal as a reflected signal via the firstline section to the first terminal by means of the partially reflectiveelement. Furthermore, the method 800 comprises passing on 806 a secondportion of the oscillation signal as a forward signal via the secondline section to the second terminal by means of the partially reflectiveelement. The method 800 furthermore comprises outputting 808 thereflected signal via a second port of a directional coupler of the firstintegrated radar circuit to a signal node of the first integrated radarcircuit. A first port of the directional coupler is coupled to the firstterminal. Furthermore, the method 800 comprises generating 810 radartransmission signals on the basis of the reflected signal by means of atleast one portion of the first transmission paths coupled to the signalnode.

Further details and aspects of the method have been described above inassociation with further exemplary embodiments (e.g. FIGS. 1 to 7). Themethod can comprise one or more optional features in accordance with thefurther exemplary embodiments.

The exemplary embodiments described herein can be summarized as follows:

Some exemplary embodiments relate to a radar system. The radar systemcomprises a first integrated radar circuit having a plurality of firsttransmission paths and a local oscillator configured to generate a localoscillator signal. The first integrated radar circuit additionally has afirst terminal configured to output an oscillation signal based on thelocal oscillator signal. The radar system furthermore comprises a secondintegrated radar circuit having at least one second transmission pathand a second terminal. Furthermore, the radar system comprises apartially reflective element coupled to the first terminal via a firstline section and to the second terminal via a second line section. Thepartially reflective element is configured to reflect back a firstportion of the oscillation signal as a reflected signal via the firstline section to the first terminal and to pass on a second portion ofthe oscillation signal as a forward signal via the second line sectionto the second terminal. The first integrated radar circuit furthermorecomprises a directional coupler, which is coupled to the first terminalvia a first port and is configured to output the reflected signal via asecond port to a signal node of the first integrated radar circuit. Thefirst transmission paths are coupled to the signal node and at least oneportion of the first transmission paths is configured to generate radartransmission signals on the basis of the reflected signal.

In accordance with some exemplary embodiments, the portion of the firsttransmission paths is configured to generate the radar transmissionsignals in a manner temporally correlated with the reflected signal,wherein the at least one second transmission path is coupled to thesecond terminal and configured to generate a radar transmission signalin a manner temporally correlated with the forward signal.

In some exemplary embodiments, the first integrated radar circuitfurthermore comprises at least one first reception path which is coupledto the signal node and is configured to down-convert a radar receptionsignal using the reflected signal.

In accordance with some exemplary embodiments, the second integratedradar circuit furthermore comprises at least one second reception pathwhich is coupled to the second terminal and is configured todown-convert a radar reception signal using the forward signal.

In some exemplary embodiments, the partially reflective element isconfigured to generate the reflected signal and the forward signal witha constant phase angle relative to one another.

In accordance with some exemplary embodiments, the partially reflectiveelement is configured to generate the reflected signal and the forwardsignal in phase.

In some exemplary embodiments, the lengths of the first line section andof the second line section are chosen such that a phase of the reflectedsignal upon reception at the first terminal is identical to a phase ofthe forward signal upon reception at the second terminal.

By way of example, in accordance with some exemplary embodiments, thefirst line section and the second line section have the same length.

In some exemplary embodiments, respective signal strengths of thereflected signal and of the forward signal differ from one another byless than 50%.

By way of example, in accordance with some exemplary embodiments,respective signal strengths of the reflected signal and of the forwardsignal are identical.

In some exemplary embodiments, the partially reflective elementcomprises exclusively passive components.

In accordance with some exemplary embodiments, the directional coupleris a rat-race coupler, wherein a biasable PIN diode is arranged betweenthe second port of the rat-race coupler and the ring conductor of therat-race coupler.

In some exemplary embodiments, one of the first transmission paths iscoupled to the first terminal via the directional coupler and isconfigured to apply the oscillation signal based on the local oscillatorsignal to the first terminal.

In accordance with some exemplary embodiments, the directional coupleris configured to receive the oscillation signal from the localoscillator via a third port and to output it to the first line via thefirst port.

In some exemplary embodiments, the radar system furthermore comprises athird integrated radar circuit having at least one third transmissionpath and a third terminal, wherein the partially reflective element iscoupled to the third terminal via a third line section. The partiallyreflective element is furthermore configured to pass on a third portionof the oscillation signal as a further forward signal via the third linesection to the third terminal. The at least one third transmission pathis coupled to the third terminal and is configured to generate a radartransmission signal in a manner temporally correlated with the furtherforward signal.

In accordance with some exemplary embodiments, the partially reflectiveelement is configured to generate the reflected signal, the forwardsignal and the further forward signal with a constant phase anglerelative to one another.

By way of example, in some exemplary embodiments, the partiallyreflective element is configured to generate the reflected signal, theforward signal and the further forward signal in phase.

In some exemplary embodiments, the third integrated radar circuitfurthermore comprises at least one third reception path which is coupledto the third terminal and is configured to down-convert a radarreception signal using the further forward signal.

In accordance with some exemplary embodiments, in a further operatingmode the local oscillator of the first integrated radar circuit isinactive, wherein the second integrated radar circuit has a furtherlocal oscillator, which in the further operating mode is configured togenerate a further local oscillator signal. The second terminal in thefurther operating mode is configured to output a further oscillationsignal based on the further local oscillator signal. The partiallyreflective element in the further operating mode is configured toreflect back a first portion of the further oscillation signal as afurther reflected signal via the second line section to the secondterminal and to pass on a second portion of the further oscillationsignal as a further forward signal via the first line section to thefirst terminal.

In some exemplary embodiments, the portion of the first transmissionpaths in the further operating mode is configured to generate the radartransmission signals in a manner temporally correlated with the furtherforward signal, wherein the at least one second transmission path in thefurther operating mode is configured to generate the radar transmissionsignal in a manner temporally correlated with the further reflectedsignal.

Further exemplary embodiments relate to an integrated radar circuit. Theintegrated radar circuit comprises a plurality of transmission paths anda local oscillator configured to generate a local oscillator signal.Furthermore, the integrated radar circuit comprises a terminal forlinking an external element via a line section. The terminal isconfigured to output an oscillation signal based on the local oscillatorsignal to the line section and to receive a portion of the oscillationsignal reflected by the external element as a reflected signal via theline section. Furthermore, the integrated radar circuit comprises adirectional coupler, which is coupled to the terminal via a first portand is configured to output the reflected signal via a second port to asignal node of the integrated radar circuit. The transmission paths arecoupled to the signal node and at least one portion of the transmissionpaths is configured to generate radar transmission signals on the basisof the reflected signal.

In accordance with some exemplary embodiments, one of the transmissionpaths is coupled to the terminal via the directional coupler and isconfigured to apply the oscillation signal based on the local oscillatorsignal to the terminal.

In some exemplary embodiments, the integrated radar circuit furthermorecomprises a switch configured to couple the local oscillator to thesignal node in a further operating mode. Said one of the transmissionpaths in the further operating mode is configured to generate a radartransmission signal on the basis of the local oscillator signal and tooutput it to the terminal. The other transmission paths in the furtheroperating mode are configured to generate the radar transmission signalson the basis of the local oscillator signal.

In accordance with some exemplary embodiments, the integrated radarcircuit furthermore comprises at least one reception path which iscoupled to the signal node and is configured to down-convert a radarreception signal using the reflected signal.

In addition, exemplary embodiments relate to a method for a radar systemhaving a first integrated radar circuit comprising at least a pluralityof first transmission paths, a local oscillator and a first terminal,and a second integrated radar circuit comprising at least one secondtransmission path and a second terminal. The method comprises outputtingan oscillation signal based on a local oscillator signal of the localoscillator via the first terminal to a partially reflective elementcoupled to the first terminal via a first line section and to the secondterminal via a second line section. Furthermore, the method comprisesreflecting back a first portion of the oscillation signal as a reflectedsignal via the first line section to the first terminal by means of thepartially reflective element. Furthermore, the method comprises passingon a second portion of the oscillation signal as a forward signal viathe second line section to the second terminal by means of the partiallyreflective element. The method furthermore comprises outputting thereflected signal via a second port of a directional coupler of the firstintegrated radar circuit to a signal node of the first integrated radarcircuit. A first port of the directional coupler is coupled to the firstterminal. Furthermore, the method comprises generating radartransmission signals on the basis of the reflected signal by means of atleast one portion of the first transmission paths coupled to the signalnode.

The cascading of a plurality of MMICs makes it possible to use morereception and/or transmission antennas for radar scanning.Correspondingly, it is possible to achieve e.g. an improvement in theradar image with regard to the azimuth angle resolution and/or theelevation angle resolution. Exemplary embodiments of the proposedsynchronization architecture can enable the use of a maximum number ofavailable transmission paths for the coupling of antennas instead of forsynchronization. This may be particularly advantageous e.g. in the caseof relatively small systems having just two or three cascaded MMICs. Asalready explained above, the phase synchronization in theradio-frequency range is important for cascaded MMICs. The proposedsynchronization architecture can enable a synchronization by means of afeedback of reflected signals to the master MMIC. In contrast toexisting approaches, one terminal of the master MMIC is sufficient forthe synchronization, such that additional antennas and/or transmissionpaths can be used for the actual radar scanning.

The aspects and features that have been described together with one ormore of the examples and figures described in detail above can also becombined with one or more of the other examples in order to replace anidentical feature of the other example or in order additionally tointroduce the feature into the other example.

The description and drawings present only the principles of thedisclosure. Furthermore, all examples mentioned here are intended to beused expressly only for illustrative purposes, in principle, in order toassist the reader in understanding the principles of the disclosure andthe concepts contributed by the inventor(s) for further development ofthe art. All statements herein regarding principles, aspects andexamples of the disclosure and also concrete examples thereof encompassthe counterparts thereof.

A block diagram can illustrate for example a rough circuit diagram whichimplements the principles of the disclosure. In a similar manner, a flowdiagram, a flow chart, a state transition diagram, a pseudo-code and thelike can represent various processes, operations or steps which arerepresented for example substantially in a computer-readable medium andare thus performed by a computer or processor, regardless of whethersuch a computer or processor is explicitly shown. Methods disclosed inthe description or in the patent claims can be implemented by acomponent having a means for performing each of the respective steps ofsaid methods.

It goes without saying that the disclosure of a plurality of steps,processes, operations or functions disclosed in the description or theclaims should not be interpreted as being in the specific order, unlessthis is explicitly or implicitly indicated otherwise, e.g. for technicalreasons. The disclosure of a plurality of steps or functions thereforedoes not limit them to a specific order unless said steps or functionsare not interchangeable for technical reasons. Furthermore, in someexamples, an individual step, function, process or operation can includea plurality of partial steps, functions, processes or operations and/orbe subdivided into them. Such partial steps can be included and be partof the disclosure of said individual step, provided that they are notexplicitly excluded.

Furthermore, the claims that follow are hereby incorporated in thedetailed description, where each claim can be representative of aseparate example by itself. While each claim can be representative of aseparate example by itself, it should be taken into considerationthat—although a dependent claim can refer in the claims to a specificcombination with one or more other claims—other examples can alsoencompass a combination of the dependent claim with the subject matterof any other dependent or independent claim. Such combinations areexplicitly proposed here, provided that no indication is given that aspecific combination is not intended. Furthermore, features of a claimare also intended to be included for any other independent claim, evenif this claim is not made directly dependent on the independent claim.

What is claimed is:
 1. A radar system, comprising: a first integratedradar circuit having a plurality of first transmission paths and a localoscillator configured to generate a local oscillator signal, wherein thefirst integrated radar circuit additionally has a first terminalconfigured to output an oscillation signal based on the local oscillatorsignal; a second integrated radar circuit having at least one secondtransmission path and a second terminal; and a partially reflectiveelement that is coupled to the first terminal via a first line sectionand to the second terminal via a second line section, wherein thepartially reflective element is configured to reflect back a firstportion of the oscillation signal as a reflected signal via the firstline section to the first terminal and to pass on a second portion ofthe oscillation signal as a forward signal via the second line sectionto the second terminal, wherein the first integrated radar circuitcomprises a directional coupler, which is coupled to the first terminalvia a first port and is configured to output the reflected signal via asecond port to a signal node of the first integrated radar circuit,wherein the plurality of first transmission paths are coupled to thesignal node, and wherein at least one portion of the plurality of firsttransmission paths is configured to generate radar transmission signalson a basis of the reflected signal.
 2. The radar system as claimed inclaim 1, wherein the at least one portion of the plurality of firsttransmission paths is configured to generate the radar transmissionsignals in a manner temporally correlated with the reflected signal, andwherein the at least one second transmission path is coupled to thesecond terminal and configured to generate another radar transmissionsignal in a manner temporally correlated with the forward signal.
 3. Theradar system as claimed in claim 1, wherein the first integrated radarcircuit comprises at least one reception path that is coupled to thesignal node and is configured to down-convert a radar reception signalusing the reflected signal.
 4. The radar system as claimed in claim 1,wherein the second integrated radar circuit comprises at least onereception path which is coupled to the second terminal and is configuredto down-convert a radar reception signal using the forward signal. 5.The radar system as claimed in claim 1, wherein: the first integratedradar circuit comprises at least one first reception path that iscoupled to the signal node and is configured to down-convert a firstradar reception signal using the reflected signal, and the secondintegrated radar circuit comprises at least one second reception pathwhich is coupled to the second terminal and is configured todown-convert a second radar reception signal using the forward signal.6. The radar system as claimed in claim 1, wherein the partiallyreflective element is configured to generate the reflected signal andthe forward signal with a constant phase angle relative to one another.7. The radar system as claimed in claim 1, wherein the partiallyreflective element is configured to generate the reflected signal andthe forward signal in phase with each other.
 8. The radar system asclaimed in claim 7, wherein: the first line section and the second linesection have a same length, and the length of the first line section andof the second line section are such that a phase of the reflected signalupon reception at the first terminal is identical to a phase of theforward signal upon reception at the second terminal.
 9. The radarsystem as claimed in claim 1, wherein respective signal strengths of thereflected signal and of the forward signal deviate from one another byless than 50%.
 10. The radar system as claimed in claim 1, whereinrespective signal strengths of the reflected signal and of the forwardsignal are identical.
 11. The radar system as claimed in claim 1,wherein the partially reflective element comprises exclusively passivecomponents.
 12. The radar system as claimed in claim 1, wherein thedirectional coupler is a rat-race coupler that comprises the second portand a ring conductor, and wherein a biasable Positive Intrinsic Negative(PIN) diode is arranged between the second port of the rat-race couplerand the ring conductor of the rat-race coupler.
 13. The radar system asclaimed in claim 1, wherein one of the plurality of first transmissionpaths is coupled to the first terminal via the directional coupler andis configured to apply the oscillation signal based on the localoscillator signal to the first terminal.
 14. The radar system as claimedin claim 1, further comprising: a third integrated radar circuit havingat least one third transmission path and a third terminal, wherein thepartially reflective element is coupled to the third terminal via athird line section, wherein the partially reflective element isconfigured to pass on a third portion of the oscillation signal as afurther forward signal via the third line section to the third terminal,and wherein the at least one third transmission path is coupled to thethird terminal and is configured to generate a further radartransmission signal in a manner temporally correlated with the furtherforward signal.
 15. The radar system as claimed in claim 14, wherein thepartially reflective element is configured to generate the reflectedsignal, the forward signal, and the further forward signal with aconstant phase angle relative to one another.
 16. The radar system asclaimed in claim 14, wherein the partially reflective element isconfigured to generate the reflected signal, the forward signal, and thefurther forward signal in phase with each other.
 17. The radar system asclaimed in claim 1, wherein: in a further operating mode, the localoscillator of the first integrated radar circuit is inactive, the secondintegrated radar circuit comprises a further local oscillator, which, inthe further operating mode, is configured to generate a further localoscillator signal, the second terminal in the further operating mode isconfigured to output a further oscillation signal based on the furtherlocal oscillator signal, the partially reflective element in the furtheroperating mode is configured to reflect back a first portion of thefurther oscillation signal as a further reflected signal via the secondline section to the second terminal and to pass on a second portion ofthe further oscillation signal as a further forward signal via the firstline section to the first terminal.
 18. The radar system as claimed inclaim 17, wherein the at least one portion of the plurality of firsttransmission paths in the further operating mode is configured togenerate the radar transmission signals in a manner temporallycorrelated with the further forward signal, and wherein the at least onesecond transmission path in the further operating mode is configured togenerate another radar transmission signal in a manner temporallycorrelated with the further reflected signal.
 19. An integrated radarcircuit, comprising: a plurality of transmission paths; a localoscillator configured to generate a local oscillator signal; a terminalfor linking an external element via a line section, wherein the terminalis configured to output an oscillation signal based on the localoscillator signal to the line section and to receive a portion of theoscillation signal reflected by the external element as a reflectedsignal via the line section; and a directional coupler that is coupledto the terminal via a first port and is configured to output thereflected signal via a second port to a signal node of the integratedradar circuit, wherein the plurality of transmission paths are coupledto the signal node and at least one portion of the plurality oftransmission paths is configured to generate radar transmission signalson a basis of the reflected signal.
 20. The integrated radar circuit asclaimed in claim 19, wherein one of the plurality of transmission pathsis coupled to the terminal via the directional coupler and is configuredto apply the oscillation signal based on the local oscillator signal tothe terminal.
 21. The integrated radar circuit as claimed in claim 20,further comprising: a switch configured to couple the local oscillatorto the signal node in a further operating mode, wherein the one of theplurality of transmission paths in the further operating mode isconfigured to generate a radar transmission signal on a basis of thelocal oscillator signal and to output the radar transmission signal tothe terminal, wherein remaining transmission paths of the plurality oftransmission paths in the further operating mode are configured togenerate the radar transmission signals on the basis of the localoscillator signal.
 22. The integrated radar circuit as claimed in claim19, further comprising: at least one reception path that is coupled tothe signal node and is configured to down-convert a radar receptionsignal using the reflected signal.
 23. A method for a radar systemhaving a first integrated radar circuit comprising a plurality of firsttransmission paths, a local oscillator, and a first terminal, and asecond integrated radar circuit comprising at least one secondtransmission path and a second terminal, the method comprising:outputting an oscillation signal based on a local oscillator signal ofthe local oscillator via the first terminal to a partially reflectiveelement coupled to the first terminal via a first line section and tothe second terminal via a second line section; reflecting back a firstportion of the oscillation signal as a reflected signal via the firstline section to the first terminal by the partially reflective element;passing on a second portion of the oscillation signal as a forwardsignal via the second line section to the second terminal by means ofthe partially reflective element; outputting the reflected signal via afirst port of a directional coupler of the first integrated radarcircuit to a signal node of the first integrated radar circuit, whereina second port of the directional coupler is coupled to the firstterminal; and generating radar transmission signals on a basis of thereflected signal at least one portion of the plurality of firsttransmission paths coupled to the signal node.